Inventive concepts relate to a nonvolatile memory device and a programming method thereof, and more particularly, to a nonvolatile memory device using incremental step pulse programming (ISPP) method and a programming method of the nonvolatile memory device.
Semiconductor memory devices may be classified into volatile memory devices, such as dynamic random-access memories (DRAMs) and/or static RAMs (SRAMs), and nonvolatile memory devices, such as electrically erasable programmable read-only memories (EEPROMs), ferroelectric RAMs (FRAMs), phase-change RAMs (PRAMs), magnetoresistive RAMs (MRAMs), and/or flash memories. Volatile memory devices may lose stored data when power is turned off, whereas nonvolatile memory devices may preserve stored data even when power is turned off.
Devices, such as MP3 players, digital cameras, mobile phones, camcorders, flash cards, and solid-state disks (SSDs), use nonvolatile memory devices. As the number of devices using nonvolatile memory devices as storage devices has increased, storage capacities of nonvolatile memory devices also have increased. One of the methods of increasing the storage capacity of a memory device is a multi-level cell (MLC) method in which a plurality of bits may be stored in one memory cell. In order to recognize data stored in an MLC, a sufficient read margin is desired to be secured. A general programming method of securing a sufficient read margin includes a programming operation based on an incremental step pulse programming (ISPP) scheme in which programming states of memory cells may be verified by using a plurality of verifying voltages whenever a programming voltage pulse is applied to the memory cells. However, even after such a verifying operation is completed, reliability of data stored in the memory cells may be reduced due to memory cell characteristics.